1. Field of the Invention
The present invention relates to a mass spectrometer and a method of mass spectrometry.
2. Discussion of the Prior Art
A common form of tandem mass spectrometry (MS/MS) involves transmitting ions emitted from an ion source through a mass filter arranged upstream of a gas collision cell. The mass filter is set so that only ions having a specific mass to charge ratio are onwardly transmitted to the gas collision cell. Ions having other mass to charge ratios are attenuated by the mass filter. Ions transmitted by the mass filter then enter the gas collision cell and are induced to fragment. Fragment ions formed within the gas collision cell exit the gas collision cell and are then mass analysed by, for example, an orthogonal acceleration Time of Flight mass analyser arranged downstream of the gas collision cell. Analysis of the fragment ions provides an effective means of identifying the parent ion which fragmented to produce the fragment ions.
A problem with known tandem mass spectrometers is that the duty cycle can be relatively poor in applications where there is a need to identify or quantify many different components from a sample. The poor duty cycle is due to the fact that whilst parent ions having a desired mass to charge ratio are transmitted through the mass filter all other parent ions are effectively attenuated by the mass filter and are lost. The duty cycle and hence sensitivity further decreases as the number of components to be analysed increases.